Check license in custom visual

Hi Together,

we are currently developing a Custom Visual.

We are wondering, how we can check the license, which the customer buyed before.

Sure we can check a key and a hash value inside the visual, but how can we check the amount of (concurring) users, which are use the visual?

Is there any information about the license possibilities? At least, when the visual is certified, there is no chance to check the

license with the help of a server etc.

Is there a option within Partner Center?

Thank you very much,

Andy